Slim Booster Bars for Electronic Devices

ABSTRACT

A wireless device includes at least one slim radiating system having a slim radiating structure and a radio-frequency system. The slim radiating structure includes one or more booster bars. The booster bar has slim width and height factors that facilitate its integration within the wireless device and the excitation of a resonant mode in the ground plane layer, and has a location factor that enables it to achieve the most favorable radio-frequency performance for the available space to allocate the booster bar. The at least one slim radiating system may be configured to transmit and receive electromagnetic wave signals in one or more frequency regions of the electromagnetic spectrum.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/274,013 filed Feb. 12, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/875,817 filed Jan. 19, 2018, issued as U.S. Pat.No. 10,236,561 on Mar. 19, 2019, which is a continuation of U.S. patentapplication Ser. No. 14/807,449 filed Jul. 23, 2015, issued as U.S. Pat.No. 9,960,478, on May 1, 2018, which claims priority under 35 U.S.C. §119(e) from U.S. Provisional Patent Application Ser. No. 62/028,494,filed Jul. 24, 2014, U.S. Provisional Patent Application Ser. No.62/064,716, filed Oct. 16, 2014, U.S. Provisional Patent ApplicationSer. No. 62/072,671, filed Oct. 30, 2014, and U.S. Provisional PatentApplication Ser. No. 62/152,991, filed Apr. 27, 2015, the entirecontents of which are hereby incorporated by reference. In addition,this application claims foreign priority under 35 U.S.C. § 119(a)-(d) toApplication No. EP 14178369.6 filed on Jul. 24, 2014, Application No. EP14189253.9 filed on Oct. 16, 2014, Application No. EP 14191145.3 filedon Oct. 30, 3014, and Application No. EP 15165167.6 filed on Apr. 27,2015, the entire contents of which are hereby incorporated by reference.

STATEMENT OF RESEARCH FUNDING

This patent application is part of a project that has received fundingfrom the European Union's Horizon 2020 Research and Innovation Programmeunder grant agreement No. 674491.

FIELD OF THE INVENTION

The present invention relates generally to the field of electronicdevices which require the transmission and/or reception ofelectromagnetic wave signals, and more particularly, to slim radiatingstructures in wireless electronic devices.

BACKGROUND

Wireless electronic devices typically handle one or more cellularcommunication standards, and/or wireless connectivity standards, and/orbroadcast standards, each standard being allocated in one or morefrequency bands, and the frequency bands being contained within one ormore regions of the electromagnetic spectrum.

For that purpose, a typical wireless electronic device must include aradiating system capable of operating in one or more frequency regionswith an acceptable radio-electric performance (in terms of for instancereflection coefficient, standing wave ratio, impedance bandwidth, gain,efficiency, or radiation pattern). The integration of the radiatingsystem within the wireless electronic device must be effective to ensurethat the overall device attains good radio-electric performance (such asfor example in terms of radiated power, received power, sensitivity)without being disrupted by electronic components and/or human loading.

Additionally, a space within the wireless electronic device is usuallylimited and the radiating system has to be included in the availablespace. The radiating system is expected to be small enough to occupy aslittle space as possible within the device, which then allows forsmaller devices, or for the addition of more specific components andfunctionalities into the device. At the same time, it is sometimesconvenient for the radiating system to be flat since this allows forslim devices. Thus, many of the demands for wireless devices alsotranslate to specific demands for the radiating systems thereof. This iseven more critical in the case in which the wireless device is amultifunctional wireless device. Commonly-owned patent applicationsWO2008/009391 and US2008/0018543 describe a multifunctional wirelessdevice. The entire disclosure of aforesaid application numbersWO2008/009391 and US2008/0018543 are hereby incorporated by reference.

For a good wireless connection, high efficiency is further required.Other more common design demands for radiating systems are thereflection coefficient (or standing-wave ratio, SWR) and the impedancewhich is supposed to be about 50 ohms. Other demands for radiatingsystems for wireless handheld or portable devices are competitive costand a low SAR.

Furthermore, a radiating system has to be integrated into a device or,in other words, a wireless device has to be constructed such that anappropriate radiating system may be integrated therein which putsadditional constraints by consideration of the mechanical fit, theelectrical fit, and the assembly fit.

Of further importance, usually, is the robustness of the radiatingsystem, which means that the radiating system does not change itsproperties upon smaller shocks to the device and the human loading.

Besides radio-frequency performance, small size and reduced interactionwith human body and nearby electronic components, one of the currentlimitations of the prior-art is that generally the antenna system iscustomized for every particular wireless handheld device model. Themechanical architecture of each device model is different and the volumeavailable for the antenna severely depends on the form factor of thewireless device model together with the arrangement of the multiplecomponents embedded into the device (e.g., displays, keyboards, battery,connectors, cameras, flashes, speakers, chipsets, memory devices, etc.).As a result, the antenna within the device is mostly designed ad hoc forevery model, resulting in a higher cost and a delayed time to market. Inturn, as typically the design and integration of an antenna element fora radiating structure is customized for each wireless device, differentform factors or platforms, or a different distribution of the functionalblocks of the device will force to redesign the antenna element and itsintegration inside the device almost from scratch.

A radiating system for a wireless handheld or portable device typicallyincludes a radiating structure comprising an antenna element whichoperates in combination with a ground plane layer providing a determinedradio-frequency performance in one or more frequency regions of theelectromagnetic spectrum. Typically, the antenna element has a dimensionclose to an integer multiple of a quarter of the wavelength at afrequency of operation of the radiating structure, so that the antennaelement is at resonance or substantially close to resonance at thefrequency of operation, and a radiation mode is excited on the antennaelement.

Antenna elements operating in multiple frequency bands allocated atdifferent regions of the electromagnetic spectrum usually presentcomplex mechanical designs and considerable dimensions, mainly due tothe fact that antenna performance is highly related to the electricaldimensions of the antenna element.

A further problem associated to the integration of the radiatingstructure, and in particular to the integration of the antenna elementin a wireless device is that the volume dedicated for such integrationhas continuously shrunk with the appearance of new smaller and/orthinner form factors for wireless devices, and with the increasingconvergence of different functionalities in a same wireless device.Therefore, from the conventional wisdom perspective, the trend inseeking for slimmer wireless device is incompatible with maximizing theperformance of a traditional antenna device, which again, it is known tohave a high correlation between antenna size (relative to the operatingwavelengths) and performance.

Some techniques to miniaturize and/or optimize the multiband behavior ofan antenna element have been described in the prior art. However theradiating structures described therein still rely on exciting aradiation mode on the antenna element for each one of the frequencybands of operation. This fact leads to complex mechanical designs andlarge antennas that usually are very sensitive to external effects (suchas for instance the presence of plastic or dielectric covers thatsurround the wireless device), to components of the wireless device(such as for instance, but not limited to, a speaker, a microphone, aconnector, a display, a shield can, a vibrating module, a battery, or anelectronic module or subsystem) placed either in the vicinity of, oreven underneath, the radiating element, and/or to the human loading. Amultiband antenna system is sensitive to any of the above mentionedaspects because they may alter the electromagnetic coupling between thedifferent geometrical portions of the radiating element, which usuallytranslates into detuning effects, degradation of the radio-frequencyperformance of the antenna system and/or the radio-frequency performanceof the wireless device, and/or greater interaction with the user (suchas an increased level of SAR).

In this sense, a radiating system such as the one described in thepresent invention not requiring a complex and/or large antenna formed bymultiple arms, slots, apertures and/or openings and a complex mechanicaldesign is preferable in order to minimize such undesired externaleffects and simplify the integration within the wireless device.

Some other attempts have focused on antenna elements not requiring acomplex geometry while still providing some degree of miniaturization byusing an antenna element that is not resonant in the one or morefrequency ranges of operation of the wireless device.

For example, WO2007/128340 discloses a wireless portable devicecomprising a non-resonant antenna element for receiving broadcastsignals (such as, for instance, DVB-H, DMB, T-DMB or FM). The wirelessportable device further comprises a ground plane layer that is used incombination with said antenna element. Although the antenna element hasa first resonant frequency above the frequency range of operation of thewireless device, the antenna element is still the main responsible forthe radiation process and for the radio-frequency performance of thewireless device. This is clear from the fact that no radiation mode canbe excited on the ground plane layer because the ground plane layer iselectrically short at the frequencies of operation (i.e., its dimensionsare much smaller than the wavelength). For this kind of non-resonantantenna elements, a matching circuitry is added for matching the antennato a level of SWR in a limited frequency range, which in this particularcase can be around SWR≤6. Such level of SWR together with the limitedbandwidth results in antenna elements which are only acceptable forreception of electromagnetic wave signals but not desirable fortransmission of electromagnetic wave signals. With such limitations,while the performance of the wireless portable device may be sufficientfor reception of electromagnetic wave signals (such as those of abroadcast service), the antenna element could not provide an acceptableperformance (for example, in terms of reflection coefficient or gain)for a communication service requiring also the transmission ofelectromagnetic wave signals.

Commonly-owned patent applications WO2008/119699 and US2010/0109955describe a wireless handheld or portable device comprising a radiatingsystem capable of operating in two frequency regions. The radiatingsystem comprises an antenna element having a resonant frequency outsidesaid two frequency regions, and a ground plane layer. In this wirelessdevice, while the ground plane layer contributes to enhance theelectromagnetic performance of the radiating system in the two frequencyregions of operation, it is still necessary to excite a radiation modeon the antenna element. In fact, the radiating system relies on therelationship between a resonant frequency of the antenna element and aresonant frequency of the ground plane layer in order for the radiatingsystem to operate properly in said two frequency regions. Nevertheless,the solution still relies on an antenna element whose size is related toa resonant frequency that is outside of the two frequency regions. Theentire disclosures of the aforesaid application numbers WO2008/119699and US2010/0109955 are hereby incorporated by reference.

A different radiating system is disclosed in U.S. Pat. No. 6,674,411, inwhich a planar inverted-L antenna (i.e., a patch antenna) has aradiating element composed by a rectangular plate placed above andsubstantially parallel to a ground plane. The antenna is connected to amatching network that provides a match in one frequency band in a firstfrequency region, and in one frequency band in a second frequencyregion. Thus the antenna system is limited to single-band operation inboth frequency regions. When operation in more bands is sought, theantenna system requires of a switched (active) matching network thatprovides non-simultaneous impedance matching in each frequency band. Soin spite of having an antenna that occupies a large volume (20×10×8mm3), not more than dual-band operation may be provided simultaneously.

For at least the above reasons, wireless device manufacturers regard thevolume dedicated to the integration of the radiating structure, and inparticular the antenna element, as being a toll to pay in order toprovide wireless communication capabilities to the handheld or portabledevice.

In order to reduce as much as possible the volume occupied into thewireless handheld or portable device, recent trends in handset antennadesign are oriented to maximize the contribution of the ground plane tothe radiation process by using very small non-resonant elements.However, non-resonant elements usually are forced to include a complexradio-frequency system. Thus, the challenge of these techniques mainlyrelies on said complexity (combination of inductors, capacitors, andtransmission lines), which is required to satisfy impedance bandwidthand efficiency specifications.

Commonly owned patent applications, WO2010/015365, and WO2010/015364 areintended for solving some of the aforementioned drawbacks. Namely, theydescribe a wireless handheld or portable device comprising a radiatingsystem including a radiating structure and a radio-frequency system. Theradiating structure is formed by a ground plane layer presentingsuitable dimensions as for supporting at least one efficient radiationmode and at least one radiation booster capable of couplingelectromagnetic energy to said ground plane layer. The radiation boosteris not resonant in any of the frequency regions of operation and,consequently, a radio-frequency system is used to properly match theradiating structure to the desired frequency bands of operation.

More particularly, in WO2010/015364 each radiation booster is intendedfor providing operation in a particular frequency region. Thus, theradio-frequency system is designed in such a way that the first internalport associated to the first radiation booster is highly isolated fromthe second internal port associated to a second radiation booster. Saidradio-frequency system usually comprises a matching network includingresonators for each one of the frequency regions of operation and a setof filters for each one of the frequency regions of operation. Thus,said radio-frequency system requires multiple stages and the performanceof the radiating systems in terms of efficiency may be affected by theadditional losses of the components. As each radiation booster isgenerally intended for providing operation in a particular frequencyregion, the bandwidth capabilities may be limited for some applicationsrequiring very wide bandwidth specially at the low frequency region, asfor example for wireless devices operating at LTE700, GSM850 and GSM900.

Commonly owned patent applications WO2014/012796 and US2014/0015730disclose a concentrated wireless device comprising a radiating systemincluding a radiating structure and a radio-frequency system, suchdevice operating two or more frequency regions of the electromagneticspectrum. A feature of said radiating system is that the operation in atleast two frequency regions is achieved by one radiation booster, or byat least two radiation boosters, or by at least one radiation boosterand at least one antenna element, wherein the radio-frequency systemmodifies the impedance of the radiating structure, providing impedancematching to the radiating system in the at least two frequency regionsof operation of the radiating system. The entire disclosure of aforesaidapplication numbers WO2014/012796 and US2014/0015730 are herebyincorporated by reference.

Commonly owned patent applications WO2014/012842 and US2014/0015728disclose very compact, small size and light weight radiation boostersoperating in single or in multiple frequency bands. Such radiationboosters are configured to be used in radiating systems that may beembedded into a wireless handheld device. Said patent applicationsfurther disclose radiation booster structures and their manufacturingmethods that enable reducing the cost of both the booster and the entirewireless device embedding said booster inside the device. The entiredisclosure of aforesaid application numbers WO2014/012842 andUS2014/0015728 are hereby incorporated by reference.

Another technique, as disclosed in U.S. Pat. No. 7,274,340, is based onthe use of two coupling elements. According to the invention, quad-bandoperation (GSM 1800/1900 and GSM850/900 bands) is provided with twocoupling elements: a low-band (LB) coupling element (for the GSM850/900bands), and a high-band (HB) coupling element (for the GSM1800/1900bands), where the impedance matching is provided through the addition oftwo matching circuits, one for the LB coupling element and another onefor the HB coupling element. In spite of using non-resonant elements,the size of the element for the low band is significantly large, being1/9.3 times the free-space wavelength of the lowest frequency for thelow frequency band. Due to such size, the low band element would be aresonant element at the high band. Additionally, the operation of thissolution is closely linked to the alignment of the maximum E-fieldintensity of the ground plane and the coupling element. The size of thelow band element undesirably contributes to increase the printed circuitboard (PCB) space required by the antenna module. According to theinvention, the bandwidth at the low frequency region is 133 MHz (from821 MHz to 954 MHz) that is insufficient for some applications requiringvery wide bandwidth, especially at the low frequency region, as forexample for wireless devices operating at LTE700, GSM850 and GSM900.

Therefore, a wireless device not requiring an antenna element andincluding a slim radiating system would be advantageous to make simplerthe integration of the slim radiating structure into the wirelesselectronic device minimizing the amount of the electronic device that isallocated towards the slim radiating system, and to provide a suitableradio-frequency performance to operate in a wide range of communicationbands. The volume freed up by the absence of a large and complex antennaelement would enable smaller and/or thinner devices, as slim electronicdevices, or even to adopt radically new form factors which are notfeasible today due to the presence of an antenna element featuring aconsiderable volume. Furthermore, by eliminating precisely the elementthat requires customization, a standard solution is sought which shouldonly require minor adjustments to be implemented in different wirelesselectronic devices.

SUMMARY

It is an object of the present invention to provide an electronic device(such as for instance but not limited to a mobile phone, a smartphone, aphablet, a PDA, an MP3 player, a headset, a USB dongle, a laptopcomputer, a tablet, a gaming device, a GPS system, a digital camera, awearable device as a smart watch, a PCMCIA, Cardbus 32 card, a sensor,or generally a multifunction wireless device which combines thefunctionality of multiple devices) containing a slim radiating systemthat covers a wide range of radio-frequencies and handles multiplecommunication bands while exhibiting a suitable radio-frequencyperformance.

It is another object of the invention to provide a slim radiating systemsuitable for being included within electronic devices, and morepreferably within slim electronic devices.

It is another object of the invention to provide a standard slimradiating system which only requires minor adjustments to be includedwithin different electronic devices.

Another object of the invention refers to the location (on the device)of radiation boosters and, more particularly, booster bars for obtainingthe most favorable frequency bandwidth values.

An electronic device according to the invention may have a candy-barshape, which means that its configuration is given by a single body. Itmay also have a two-body configuration such as a clamshell, flip-type,swivel-type or slider structure. In some other cases, the device mayhave a configuration comprising three or more bodies. It may further oradditionally have a twist configuration in which a body portion (e.g.with a screen) can be twisted (i.e., rotated around two or more axes ofrotation which are preferably not parallel). The electronic device maycomprise a memory module, a processing circuitry module, a userinterface module, a battery, and a wireless communication module.

The wireless communication module may include a slim radiating system, aradio-frequency transceiver circuit, a power amplifier circuit and abase-band module. The slim radiating system may be coupled to the poweramplifier via a conductive path and to the radio transceiver circuit viaa conductive path. The wireless communication module may include amultiplexing stage coupled to the slim radiating system via a conductivepath.

A slim radiating system in accordance with the invention may include aslim radiating structure, a radio-frequency system, at least oneinternal conductive path and at least one external conductive path. Theslim radiating structure may include a ground element and at least oneradiation booster, which in some embodiments may be a booster bar,separated from the ground element by a gap.

A slim radiating structure may comprise a ground element and one, two,three, four or even more radiation boosters. In some preferredembodiments, said radiation boosters may be booster bars featuring anelongated shape. In preferred embodiments, each booster bar or radiationbooster is separated from the ground element by a gap.

An aspect of the present invention relates to the use of the groundelement (or ground plane layer) of the slim radiating system as a mainsource of radiation.

A radiation booster includes a dielectric material and in someembodiments, a single standard layer of dielectric material spacing twoor more conductive elements. A single standard layer of dielectricmaterial refers to dielectric material with a standard thickness, whichis available off-the-shelf. For example, 0.025″ (0.635 mm), 0.047″ (1.2mm), 0.093″ (2.36 mm) or 0.125″ (3.175 mm) are common/standardthicknesses for dielectric materials which are available in the market.Examples of dielectric materials may include fiber-glass FR4, Cuclad,Alumina, Kapton, Ceramic and for instance commercial laminates andsubstrates from Rogers® Corporation (RO3000® and RO4000® laminates,Duroid substrates and alike) or other suitable non-conductive materials.

The radiation booster may be formed by printing or depositing conductivematerial in a first and a second surface of the dielectric material(e.g. top and bottom) and adding several vias to electrically connectthe conductive material in the first surface with the conductivematerial in the second surface. The conductive material in the first andsecond surfaces may have a substantially polygonal shape. Some possiblepolygonal shapes are for instance, but not limited to, squares,rectangles, and trapezoids. When the conductive material in said firstand second surfaces has an elongated shape, for instance a rectangularshape, the radiation booster takes the form of a booster bar; a boosterbar may also include vias that electrically connect the conductivematerial in the first surface with the conductive material in the secondsurface.

The elongated shape of a booster bar is characterized by two slim formfactors: a slim width factor and a slim height factor. The slim widthfactor is a ratio between a length of the booster bar and a width of thebooster bar. The slim height factor is a ratio between the length of thebooster bar and a height of the booster bar.

The slim width factor characterizes the ratio between the length and thewidth of the booster bar, whereas the slim height factor characterizesthe ratio between the length and the height of the booster bar. In apreferred embodiment, the value for the slim width factor and the slimheight factor is greater than 2, for instance in one or more of thoseembodiments the value for the slim width factor is greater than 3, andpreferably larger than 3.5, and the slim height factor is greater than4. In another preferred embodiment, the value for the slim width factoris greater than 6 and/or the slim height factor is greater than 6. Inanother preferred embodiment, the value for the slim width factor isgreater than 6 and/or the slim height factor is larger than 9. In someless preferred embodiments, the values for both the slim width factorand the slim height factor are between 1 and 2. The slim width factorand the slim height factor of a booster bar may take any of the valueslisted above yet being smaller than 25, and preferably smaller than 10.

A radiation booster may comprise one, two or more booster barselectrically connected, forming a booster element that fits in animaginary sphere having a diameter smaller than ⅓ of a radianspherecorresponding to the lowest frequency of operation of the slim radiatingsystem. Such a booster element may also be characterized by a slim widthfactor, a slim height factor, and a location factor. Any booster elementaccording to the present invention may be limited by a slim width factorand a slim height factor, each of these factors being between 1 and 10,and preferably between 2 and 10.

An advantageous aspect of the invention refers to a booster bar built ona single standard layer of dielectric material that is manufactured at acompetitive cost.

Another advantageous aspect of the invention refers to a booster barhaving a slim width factor and/or slim height factor that enables thebooster bar to occupy only a small portion within the electronicwireless device and making it suitable for its integration within slimelectronic devices or flexible electronic devices.

Another advantageous aspect of the present invention refers to thelocation and slim form factors of a booster bar to guarantee the mostadvantageous frequency bandwidth for the available space.

A radiation booster, like for instance a booster bar, is separated fromthe ground plane layer by a gap. In the context of this document, thegap refers to a minimum distance between a point at an edge of theground plane layer and a point at an edge of the bottom conductivesurface of the radiation booster. The location of the radiation boosteris characterized by a location factor that is a ratio between the widthof the radiation booster and the gap. In a preferred example, thelocation factor is between 0.5 and 2. In another preferred example, thelocation factor is between 0.3 and 1.8.

Each radiation booster of the slim radiating system advantageouslycouples the electromagnetic energy from the radio-frequency system tothe ground element in transmission, and from the ground element to theradio-frequency system in reception. The radiation boosters excite aradiation mode in the ground element enabling the radiation from theground element.

The form factor of the radiation booster, together with its location inrelation to the ground element, is configured to achieve a properexcitation of the radiation mode of the ground element. The locationfactor is selected to achieve the most favorable frequency bandwidth fora radiation booster with a certain form factor, particularly a boosterbar.

Apart from the form factor of the radiation booster, the gap is alsorelevant for properly exciting a radiation mode in the ground planelayer and to achieve the most advantageous frequency bandwidth. Thebandwidth of the slim radiating system may be degraded if the locationfactor is not properly selected.

The location factor and the slim form factors of a booster bar areselected to ensure the most favorable frequency bandwidth whileminimizing/reducing the amount of space allocated towards theintegration of the booster bar within the electronic device.

The slim radiating structure is mounted within the electronic device andis coupled to the radio-frequency system via a conductive path. Theradiation booster is coupled to the ground element via a conductive pathand is located at certain distance from the ground element. Saidconductive path comprises a conductive element which may be linear orinclude a surface; the conductive element may comprise, for instance butnot limited to, a metallic strip and/or a conductive trace.

In some embodiments, a slim radiating structure comprises one groundelement or conductive material acting as a ground plane for the slimradiating structure. In some other embodiments, a slim radiatingstructure may comprise two, three or more ground elements or conductivematerials acting as a ground plane for the radiating structure. In suchembodiments, the plurality of ground elements may be electricallyinterconnected one to each other.

The at least one radiation booster for a slim radiating structureaccording to the present invention may have a maximum size at leastsmaller than 1/15 of the free-space wavelength corresponding to thelowest frequency of the first frequency region of operation. In somecases, said maximum size may be also smaller than 1/20, and/or 1/25,and/or 1/30, and/or 1/50, and/or 1/100 of the free-space wavelengthcorresponding to the lowest frequency of the first frequency region ofoperation. In some cases, the at least one radiation booster fits in animaginary sphere having a diameter smaller than ⅓, or preferably smallerthan ¼, or preferably smaller than ⅙, or even more preferably smallerthan 1/10 of a radiansphere at said free-space wavelength. Theradiansphere is defined as an imaginary sphere having a radius equal tothe operating wavelength divided by two times π (pi).

Furthermore, in some examples, the at least one radiation booster alsohas a maximum size smaller than 1/15, and/or 1/20, and/or 1/25, and/or1/30, and/or 1/50 of the free-space wavelength corresponding to thelowest frequency of the second frequency region of operation. In somecases, the at least one radiation booster fits in an imaginary spherehaving a diameter smaller than ⅓, or preferably smaller than ¼, orpreferably smaller than ⅙, or even more preferably smaller than 1/10 ofa radiansphere at said free-space wavelength.

Additionally, in some of these examples the at least one radiationbooster has a maximum size larger than 1/1400, 1/700, 1/350, 1/250,1/180, 1/140, or 1/120 times the free-space wavelength corresponding tothe lowest frequency of said first frequency region.

The maximum size of a radiation booster is preferably defined by thelargest dimension of a booster box that completely encloses saidradiation booster, and in which the radiation booster is inscribed. Morespecifically, a booster box for a radiation booster is defined as beingthe minimum-sized parallelepiped of square or rectangular faces thatcompletely encloses the radiation booster and wherein each one of thefaces of said minimum-sized parallelepiped is tangent to at least apoint of said radiation booster. Moreover, each possible pair of facesof said minimum-size parallelepiped sharing an edge forms an inner angleof 90°. In those cases in which the radiating structure comprises morethan one radiation booster, a different booster box is defined for eachof them.

In some preferred examples, the area defined by the two largestdimensions of a booster box is advantageously small compared to thesquare of the wavelength corresponding to the lowest frequency of thefirst frequency region; in particular, a ratio between said area and thesquare of the wavelength corresponding to the lowest frequency of thefirst frequency region may be advantageously smaller than at least oneof the following percentages: 0.15%, 0.12%, 0.10%, 0.08%, 0.06%, 0.04%,or even 0.02%. In some of these examples, a ratio between the areadefined by the two largest dimensions of a booster box and the square ofthe wavelength corresponding to the lowest frequency of the secondfrequency region may also be advantageously smaller than at least one ofthe following percentages: 0.50%, 0.45%, 0.40%, 0.35%, 0.30%, 0.25%,0.20%, 0.15%, 0.10%, or even 0.05%.

Moreover, in some embodiments according to the present invention, the atleast one radiation booster will entirely fit inside a limiting volumeequal or smaller than L3/25000, and in some cases equal or smaller thanL3/50000, L3/100000, L3/150000, L3/200000, L3/300000, L3/400000, or evensmaller than L3/500000, being L the wavelength corresponding to thelowest frequency of the first frequency region of operation.

A slim radiating system according to the invention is configured tohandle multiple communication bands, and to provide coverage and anacceptable level of reflection coefficient in a wide range ofcommunication bands in one or more frequency regions of operationexhibiting a suitable radio-frequency performance. The slim radiatingsystem is designed to transmit and receive radio-frequency signals inmultiple communication bands of interest, including frequency bands thatmay be added, for instance, through the deployment of future cellulartelephone bands and/or data service bands.

In the context of this document, a frequency band preferably refers to arange of frequencies used by a particular cellular communicationstandard, a wireless connectivity standard or a broadcast standard,while a frequency region preferably refers to a continuum of frequenciesof the electromagnetic spectrum. For example, the GSM 1800 standard isallocated in a frequency band from 1710 MHz to 1880 MHz while the GSM1900 standard is allocated in a frequency band from 1850 MHz to 1990MHz. A device operating the GSM 1800 and the GSM1900 standards must havea radiating system capable of operating in a frequency region from 1710MHz to 1990 MHz. As another example, a wireless device operating the GSM850 standard (allocated in a frequency band from 824 MHz to 894 MHz) andthe GSM 1800 standard must have a radiating system capable of operatingin two separate frequency regions.

Some frequency bands that the slim radiating system may be configured totransmit and receive signals in are, for example, GSM 850 (824-894 MHz),GSM 900 (880-960 MHz), GSM 1800 (1710-1880 MHz), GSM 1900 (1850-1990MHz), WCDMA 2100 (1920-2170 MHz), CDMA 1700 (1710-2155 MHz), LTE 700(698-798 MHz), LTE 800 (791-862 MHz), LTE 2600 (2500-2690 MHz), LTE 3500(3.4-3.6 GHz), LTE 3700 (3.6-3.8 GHz), WiFi or WLAN (2.4-2.5 GHz and/or4.9-5.9 GHz), etc. A wireless handheld or portable device according tothe present invention may operate one, two, three, four or more cellularcommunication standards, wireless connectivity standards, and/orbroadcasts standards, each standard being allocated in one, two or morefrequency bands, and said frequency bands being contained within one,two or more frequency regions of the electromagnetic spectrum.

The slim radiating system is designed to provide an acceptable level ofreflection coefficient in the frequency regions of operation. A slimradiating system according to the present invention is configured tooperate in at least one frequency region. In some embodiments, the slimradiating system is configured to operate in a first frequency regioncomprising at least a first frequency band, and a second frequencyregion comprising at least a second frequency band. Such radiatingsystem is configured to satisfy the radio-frequency bandwidths andfrequency coverage goals. A slim radiating system according to thepresent invention may advantageously feature an impedance bandwidth inthe first frequency region larger than 5%, 10%, 15%, or even larger than20%. In addition, such radiating system may also feature an impedancebandwidth in the second frequency region larger than 5%, 10%, 15%, 20%,25%, 30%, 35%, or even larger than 40%. The impedance bandwidth isdefined as the difference between the highest and lowest frequencies ofa frequency region, divided by the central frequency of the samefrequency region.

Due to the small size of the radiation boosters, the radiation boostersand booster bars may be electrically short at some or all frequencies ofoperation. A slim radiating structure according to the present inventionmay feature a first resonant frequency, measured at an internal path, ata frequency higher (i.e. above) than the highest frequency of the firstfrequency region of operation when said radio-frequency system isdisconnected. Moreover, when the radio-frequency system is disconnected,the input impedance of the slim radiating structure measured at theinternal path may have an important reactance, in particular acapacitive reactance, within the frequencies of said first frequencyregion. In this case, a ratio between the first resonant frequency ofthe slim radiating structure and the highest frequency of the firstfrequency region is advantageously greater than 1.2. In some cases, saidratio may be even greater than one or more of the following values: 1.5,1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or 3.0. In some examples, a ratio betweensaid first resonant frequency and the lowest frequency of the firstfrequency region of operation is advantageously greater than 1.3, oreven greater than one or more of the following values: 1.4, 1.5, 1.8,2.0, 2.2, 2.4, 2.6, 2.8, or 3.0.

In some embodiments, the first resonant frequency of the slim radiatingstructure, measured at an internal path when the radio-frequency systemis disconnected, is above the highest frequency of the second frequencyregion, wherein a ratio between said first resonant frequency and saidhighest frequency of the second frequency region may be larger than oneor more of the following values: 1.0, 1.1, 1.2, 1.4, 1.6, 1.8, or 2.0.In some other embodiments, said first resonant frequency is within thesecond frequency region. In some other examples, said first resonantfrequency is above the highest frequency of the first frequency regionand below the lowest frequency of the second frequency region.

In the context of this document, a resonant frequency associated to aradiation booster of the slim radiating structure preferably refers to afrequency at which the input impedance of the slim radiating structure,the impedance being measured at the internal path coupling the radiationbooster to the radio-frequency system when the radio-frequency system isnot connected, has an imaginary part equal or substantially equal tozero.

The radio-frequency system may comprise one or more matching circuitsthat modify the impedance of the slim radiating structure providingimpedance matching to the slim radiating system, at an external path, inone or more frequency regions of operation of the slim radiating system.

A radio-frequency system according to the invention may include at leastone matching network with a plurality of stages, for instance, two,three, four, five, six or more stages. A stage comprises one or morecircuit components (for example but not limited to, inductors,capacitors, resistors, jumpers, short-circuits, delay lines, or otherreactive or resistive components). In some cases, a stage has asubstantially inductive behavior in the frequency region or regions ofoperation of the slim radiating system, while another stage has asubstantially capacitive behavior in said frequency region/s, and yet athird one may have a substantially resistive behavior in said frequencyregion/s. In an example, a stage may substantially behave as a resonantcircuit (such as, for instance, a parallel LC resonant circuit or aseries LC resonant circuit) in at least one frequency region ofoperation of the slim radiating system. The use of stages having aresonant circuit behavior allows one part of a given matching network beeffectively connected to another part of said matching network for agiven range of frequencies, or in a given frequency region, and beeffectively disabled for another range of frequencies, or in anotherfrequency region.

In some examples, the at least one matching network alternates stagesconnected in series (i.e. cascaded) with stages connected in parallel(i.e. shunted), forming a ladder structure. In some cases, a matchingnetwork comprising two stages forms an L-shaped structure (i.e.series-parallel or parallel-series). In some cases, a matching networkcomprising three stages forms either a pi-shaped structure (i.e.parallel-series-parallel) or a T-shaped structure (i.e.series-parallel-series).

In some embodiments, a radio-frequency system according to the presentinvention comprises a matching circuit in a ladder topology. Suchmatching circuit preferably comprises one reactive component per stage.In some other embodiments, a radio-frequency system according to thepresent invention comprises a matching circuit at least including aseries LC resonant circuit and a parallel LC resonant circuit.

In a preferred embodiment, an electronic device comprises a slimradiating system configured to transmit and receive electromagnetic wavesignals in at least one frequency region of the electromagneticspectrum, and comprising a slim radiating structure, a radio-frequencysystem, at least one internal conductive path and at least one externalconductive path. The slim radiating structure comprises at least oneground element and at least one booster bar. The at least one internalconductive path comprises a conductive element that couples the at leastone booster bar to the radio-frequency system. The radio-frequencysystem comprises at least one matching circuit modifying the impedanceof the slim radiating structure providing impedance matching to the slimradiating system in the at least one frequency region at the at leastone external conductive path. The at least one booster bar has anelongated shape, and is characterized by a slim width factor greaterthan 3 and a slim height factor greater than 3, is separated from the atleast one ground element by a gap and is characterized by a locationfactor between 0.5 and 2.

Another preferred embodiment relates to an electronic device including aslim radiating system that comprises a slim radiating structure, aradio-frequency system, an internal conductive path and at least oneexternal conductive path; the slim radiating system is configured totransmit and receive electromagnetic wave signals in a first frequencyregion and a second frequency region. The slim radiating structurecomprises at least one ground element, and one booster bar separatedfrom the ground element by a gap and is characterized by a locationfactor between 0.3 and 1.8. The internal conductive path comprises aconductive element that couples the booster bar to the radio-frequencysystem. The radio-frequency system comprises a matching circuit thatmodifies the impedance of the slim radiating structure providingimpedance matching to the slim radiating system in the first and secondfrequency regions at the at least one external conductive path. Thefirst and second frequency regions are preferably separated so that thelowest frequency of the second frequency region is above the highestfrequency of the first frequency region. Some preferred matchingcircuits for such preferred embodiment are described in FIGS. 15A-15F.

Further, an advantageous aspect of the invention refers to aradio-frequency system comprising a matching circuit that providesimpedance matching to the slim radiating system in first and secondfrequency regions preferably not requiring a filtering circuit orcomponent that separates frequencies of the first frequency region fromfrequencies of the second frequency region (e.g. a diplexer, a bank offilters, etc.) for providing impedance matching in the first frequencyregion and second frequency region independently (i.e. in two separatebranches or paths). Thus preferred matching circuits may provideimpedance matching in said first and second frequency regions with onebranch.

According to the present invention, some preferred matching circuitspreferably comprise seven or less components, for instance: two, three,four, five, six or seven. Such matching circuits preferably do notcomprise active circuits or components.

In some embodiments in which the slim radiating system is configured totransmit and receive signals in a first frequency region and a secondfrequency region, a ratio between the lowest frequency of the secondfrequency region and the lowest frequency of the first frequency regionmay be greater than 1.5. In some of these embodiments, said ratio may bealso greater than 1.8, 2.0, 2.2, or 2.4. In addition, in someembodiments in which the slim radiating system is configured to operatesignals from first and second frequency regions, a ratio between thelowest frequency of the second frequency and the highest frequency ofthe first frequency region may be greater than 1.2, 1.5, 1.8, 2.0, 2.2,or 2.4.

Accordingly, an advantageous aspect of such radio-frequency system isits efficiency in that impedance matching in the first and secondfrequency regions may be provided with one matching circuit using areduced number of components, which consequently introduces lower lossesin the radio-frequency system and makes it more robust against thetolerances of the components. Moreover, by not including filteringcircuits such as diplexers, the radio-frequency system avoids theinsertion losses characterizing such type of circuits and the necessityof having two separate matching circuits, which consequently makes theradio-frequency system have less components and the slim radiatingsystem smaller in terms of area occupied in the device.

In a third preferred embodiment, an electronic device includes a slimradiating system comprising a slim radiating structure, aradio-frequency system, first and second internal conductive paths andat least one external conductive path; the slim radiating system isconfigured to transmit and receive electromagnetic wave signals in afirst frequency region and a second frequency region. The slim radiatingstructure comprises at least one ground plane layer, first and secondradiation boosters, each of the first and second radiation boostersbeing separated from the ground plane layer by a gap. The first internalconductive path comprises a conductive element that couples the firstradiation booster to the radio-frequency system, and the second internalconductive path comprises a conductive element that couples the secondradiation booster to the radio-frequency system. The radio-frequencysystem comprises a matching circuit coupled to the first and secondinternal conductive paths and to the external conductive path, thematching circuit modifies the impedance of the slim radiating structureproviding impedance matching to the slim radiating system in the firstand second frequency regions.

In some cases, the slim radiating system may comprise a first externalconductive path and a second external conductive path, and theradio-frequency system may include a diplexer circuitry thatadvantageously filters signals from first and second frequency regions,said signals being matched in impedance in the first and secondfrequency regions by the matching circuit within the radio-frequencysystem. A first port of the diplexer is connected to the matchingcircuit, and the two remaining ports of the diplexer are connected tothe first and second external conductive paths. The first and secondexternal paths comprise, respectively, signals for frequencies from thefirst frequency region, and signals for frequencies from the secondfrequency region.

A further aspect of the present invention relates to a test platform forelectromagnetically characterizing radiation boosters. Said platformcomprises a substantially square conductive surface on top of which, andsubstantially close to the central point, the element to becharacterized is mounted perpendicular to said surface in a monopoleconfiguration, said conductive surface acting as the ground plane.

The substantially square conductive surface comprises sides with adimension larger than a reference operating wavelength. In the contextof the present invention, said reference operating wavelength is thefree-space wavelength equivalent to a frequency of 900 MHz. Asubstantially square conductive surface according to the presentinvention is made of copper with sides measuring 60 centimeters, and athickness of 0.5 millimeters.

In the test configuration as set forth above, a booster bar according tothe present invention may be characterized by a ratio between the firstresonance frequency and the reference frequency (900 MHz) being largerthan a minimum ratio of 3.0. In some cases, said ratio may be evenlarger than a minimum ratio such as: 3.4, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8,5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.6 or 7.0.

A booster bar according to the present invention may also becharacterized by a radiation efficiency measured in said platform, at afrequency equal to 900 MHz, being less than 50%, preferably being lessthan 40%, 30%, 20%, or 10%, and in some cases being less than 7.5%, 5%,or 2.5%. All those are quite remarkably low efficiency valuesconsidering the additional 1:3 frequency mismatch and beyond obtained insome of the embodiments as described above. Such a frequency shift wouldintroduce further mismatch losses that would result in an overallantenna efficiency below 5%, and quite typically below 2%, which wouldbe ordinarily considered unacceptable for a mobile phone or wirelessapplication. Still, quite surprisingly, when combining at least onebooster bar with the radio-frequency system of a slim radiating systemaccording to the present invention, said slim radiating system recoversthe efficiency required for the performance of a typical wirelessdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are shown in the enclosed figures.

FIGS. 1A-1B—Show examples of wireless handheld devices including slimradiating systems according to preferred embodiments of the invention.

FIGS. 2A-2D—Block diagram representations of five examples of slimradiating systems in according with some preferred embodiments of thepresent invention.

FIG. 3—Shows a perspective view of an example of a slim radiatingstructure including a booster bar in accordance with the presentinvention.

FIGS. 4A-4B—Graphs showing bandwidth performances of several slimradiating systems as a function of the booster bar's width and gapdimensions.

FIG. 5—Graph showing bandwidth performances of a slim radiating systemas a function of the booster bar's width and gap dimensions for threedifferent depth values.

FIG. 6—Graph showing an example of an acceptable radio-electricfrequency behavior for a slim radiating system in accordance with thepresent invention.

FIG. 7—Shows a perspective view of an example of slim radiatingstructure including four booster bars in accordance with a preferredembodiment.

FIG. 8—Plan view of an exemplary radio-frequency system coupled to aslim radiating structure in accordance with the present invention.

FIG. 9—Graph showing the radio-electric frequency behavior of a slimradiating system including the slim radiating structure of FIG. 7 andthe radio-frequency system of FIG. 8.

FIG. 10—Perspective view of an exemplary slim radiating structureincluding three booster bars in accordance with a preferred embodiment.

FIG. 11—Plan view of an example of a radio-frequency system coupled to aslim radiating structure in accordance with the present invention.

FIG. 12—Graph showing the radio-electric frequency behavior of a slimradiating system including the slim radiating structure of FIG. 10 andthe radio-frequency system of FIG. 11.

FIG. 13—Shows another exemplary slim radiating structure according tothe invention.

FIGS. 14A-14B—Show schematic representations of radio-frequency systemsin accordance with a preferred embodiment.

FIGS. 15A-15F—Show six preferred matching circuits for some embodimentsof the present invention.

FIGS. 16A-16F—Show the impedance transformation of an exemplary slimradiating system as the different stages of a matching circuit in theradio-frequency system are added.

FIG. 17—Shows the reflection coefficient of exemplary slim radiatingsystem of FIG. 16F.

FIG. 18A-18B—Show the impedance and the reflection coefficient of anexemplary slim radiating system comprising a radio-frequency systemaccording to the invention.

FIG. 19—Shows an exemplary radiation booster according to the invention.

FIG. 20—Shows a slim radiating structure and an internal path in theform of a conductive trace in accordance with a preferred embodiment.

FIG. 21A-21B—Show a test platform for the electromagneticcharacterization of radiation boosters.

FIG. 22—Shows the radiation efficiency and antenna efficiency of aradiation booster according to the present invention measured with thetest platform depicted in FIGS. 21A and 21B.

DETAILED DESCRIPTION

Further characteristics and advantages of the invention will becomeapparent in view of the detailed description of some preferredembodiments which follows. Said detailed description of some preferredembodiments of the invention is given for purposes of illustration onlyand in no way is meant as a definition of the limits of the invention,made with reference to the accompanying figures.

Illustrative wireless electronic devices including a slim radiatingsystem in accordance with the present invention are shown in FIGS. 1Aand 1B. In the particular arrangement of FIG. 1A, the wirelesselectronic device 100 is a smartphone although it might represent otherwireless electronic devices such as for instance a phablet or a tablet.The slim radiating system includes a first booster bar 101, a secondbooster bar 102, a booster element 110, and a ground element 105 (whichmay be included in a layer of a multilayer printed circuit board). Thebooster element 110 comprises two contiguous booster bars: the thirdbooster bar 103 and the fourth booster bar 104. The first booster bar101 is coupled to a radio-frequency system 109 via a conductive path106, the second booster bar 102 is coupled to the radio-frequency system109 via a conductive path 107, and the booster element 110 is coupled tothe radio-frequency system 109 via a conductive path 108.

In FIG. 1B there is shown a wireless handheld device 150 in an explodedperspective view, the device comprises a slim radiating structure and aradio-frequency system 153. The slim radiating structure comprises aradiation booster 151 taking the form of a booster bar with an elongatedshape, and a ground plane layer 152. The booster bar 151 is coupled tothe radio-frequency system via the internal conductive path 154 which,in this particular example, may be a conductive trace.

In the examples of FIGS. 1A and 1B, the booster bars are arranged on apart of the device free of ground plane, so there is no ground plane inthe orthogonal projection of the booster bars onto the plane comprisingthe ground plane layers 105 and 152, respectively. In other embodiments,the orthogonal projection of a booster bar or other radiation boosteronto the plane comprising the ground plane layer may be overlappedpartially or completely by the ground plane layer.

FIG. 2A shows a block diagram representation of a slim radiating systemfor an electronic device. The slim radiating system 201 a comprises slimradiating structure 202 a, radio-frequency system 203 a, internalconductive path 204 a, and external conductive path 205 a. The slimradiating structure is coupled to the radio-frequency system via theinternal path 204 a, and to other RF circuitry for handling RF wavesignals via the external path 205 a. A slim radiating system inaccordance with this block diagram is configured to operate in at leastone frequency region, or in at least two frequency regions, or in atleast three frequency regions.

FIG. 2B shows another block diagram of a slim radiating system for anelectronic device according to the present invention. The slim radiatingsystem 201 b comprises slim radiating structure 202 b, radio-frequencysystem 203 b, two internal conductive paths 204 b and 205 b, and twoexternal conductive paths 206 b and 207 b. The slim radiating structureis coupled to the radio-frequency system via the internal paths 204 band 205 b, and to other RF circuitry for handling RF wave signals viathe external paths 206 b and 207 b. A slim radiating system inaccordance with this block diagram is configured to operate in at leasttwo frequency regions, or in at least three frequency regions.

FIG. 2C shows another block diagram of a slim radiating system for anelectronic device according to the present invention. The slim radiatingsystem 201 c comprises slim radiating structure 202 c, radio-frequencysystem 203 c, three internal conductive paths 204 c, 205 c and 206 c,and three external conductive paths 207 c, 208 c, and 209 c. The slimradiating structure is coupled to the radio-frequency system via theinternal conductive paths 204 c, 205 c and 206 c, and to other RFcircuitry for handling RF wave signals via the external conductive paths207 c, 208 c and 209 c. A slim radiating system in accordance with thisblock diagram is configured to operate in at least three frequencyregions.

FIG. 2D shows another block diagram of a slim radiating system for anelectronic device according to the present invention. The slim radiatingsystem 201 d is similar to 201 a from FIG. 2A. It comprises slimradiating structure 202 a, radio-frequency system 203 d, internalconductive path 204 a, and two external conductive paths 205 d and 206d. The slim radiating structure is coupled to the radio-frequency systemvia the internal paths 204 a, and to other RF circuitry for handling RFwave signals via the external paths 205 d and 206 d. The radio-frequencysystem 203 d may comprise a matching circuit configured to provideimpedance matching in at least two frequency regions, and a diplexer maybe connected to said matching circuit and coupled to the external paths.A slim radiating system in accordance with this block diagram isconfigured to operate in at least two frequency regions. Theradio-frequency system 203 d is convenient for the interconnection withan RF (radio-frequency) front-end module or RF circuitry that includesseparate inputs for signals from the first frequency region and thesecond frequency region. If such RF front-end module (not illustrated)had one input/output for all the signals, the radio-frequency system 203a from FIG. 2A would be more suitable.

FIG. 3 illustrates a preferred example of a slim radiating structure 301according to the present invention. The slim radiating structurecomprises a booster bar 303 and a ground plane layer 302, the boosterbar comprises a single standard layer of dielectric material 306 with atop 304 and a bottom 305 conductive surfaces. The booster bar has alength 310, a width 311 and a height 312. The length of the booster baris taken along the dimension that is substantially parallel to theground plane layer in the top or bottom conductive surface, the width istaken along the dimension that is substantially perpendicular to theground plane layer in the top or bottom conductive surface, and theheight is taken as the minimum distance between the top conductivesurface and the bottom conductive surface. In some embodiments thebooster bar comprises pads on a first and a second surface so that themounting of the booster can be reversed and top and bottom sides can beinterchanged.

The size and shape of the booster bar is characterized by a slim widthfactor and a slim height form factor. The slim width factor is a ratiobetween the length and the width of the booster bar, and the slim heightfactor is a ratio between the length and height of the booster bar,being the slim width factor and the slim height factor preferably largerthan 3. In this example, where the booster is configured to operate inone or more frequency bands within the 600 MHz-6 GHz range (e.g. GSM 850(824-894 MHz), GSM 900 (880-960 MHz), GSM 1800 (1710-1880 MHz), GSM 1900(1850-1990 MHz), WCDMA 2100 (1920-2170 MHz), CDMA 1700 (1710-2155 MHz),LTE 700 (698-798 MHz), LTE 800 (791-862 MHz), LTE 2600 (2500-2690 MHz),LTE 3500 (3.4-3.6 GHz), LTE 3700 (3.6-3.8 GHz), WiFi (2.4-2.5 GHz and/or4.9-5.9 GHz)), the length is 10 millimeters, the width is 3.2millimeters and the height is 3.2 millimeters, being the slim widthfactor 3.125 and the slim height factor 3.125, all those dimensions inthese and other embodiments, within a typical tolerance of, for instance+/−1%-3% and in some occasions up to a 10% variation. The booster bar isseparated from the ground plane by a gap 313; the gap is taken as theminimum distance between the bottom conductive layer and the groundplane layer. The gap distance plus the booster bar's width 311 ischaracterized as the depth of the radiation booster. The location of thebooster bar in relation to the ground plane layer is characterized by alocation factor. The location factor is a ratio between the width of thebooster bar and the gap, being the location factor preferably in therange of between 0.5 and 2. In this example, the width is 3.2 mm and thegap is 3.3 mm, being the location factor 0.96 and the depth 6.5 mm, allthose dimensions within a typical tolerance of, for instance +/−10%variation.

FIG. 4A and FIG. 4B illustrate two examples of the relevance of thelocation and width of the booster bar in the radio-frequency performanceof the slim radiating system; the radio-frequency performance of theslim radiating system is affected by the location of the booster barwith respect to the ground plane layer and the width of the booster bar.FIG. 4A and FIG. 4B plot the potential bandwidths achieved by six slimradiating systems as a function of the booster bar's width and gapdimensions. Curve 401 represents the potential bandwidth of a slimradiating system comprising a booster bar characterized by a height of2.4 mm and a length of 11.5 mm. Curve 402 represents the potentialbandwidth of a slim radiating system that includes a booster bar havinga height of 3.2 mm and a length of 9 mm. Curve 403 represents thepotential bandwidth of a slim radiating system comprising a booster barcharacterized by a height of 2.4 mm and a length of 10.5 mm. Curve 404represents the potential bandwidth of a slim radiating system comprisinga booster bar characterized by a height of 3.2 mm and a length of 7 mm.Curve 405 represents the potential bandwidth of a slim radiating systemcomprising a booster bar characterized by a height of 2.4 mm and alength of 9 mm. Curve 406 represents the potential bandwidth of a slimradiating system comprising a booster bar characterized by a height of2.4 mm and a length of 7 mm. As shown in FIG. 4A and FIG. 4B, thepotential bandwidth of the slim radiating system depends on the widthdimension of the booster bar and the location of the booster bar inrelation to the ground plane layer; for each of the curves, there is aregion where the most favorable bandwidth values are achieved. In thisinvention, such region is referred as the effective bandwidth regionwhich corresponds to a range of location factor values that provide theregion of most advantageous bandwidth values for the slim radiatingsystem. The preferred values for the location factor are in the range ofbetween 0.5 and 2. Such result is against conventional wisdom as thewider the width of the antenna element, the greater the bandwidth as,for example, in a monopole antenna.

FIG. 5 illustrates another example of the effect of the booster bar'slocation and width on the radio-frequency performance of a slimradiating system; the radio-frequency performance of the slim radiatingsystem is affected by the location of the booster bar with respect tothe ground plane layer and the width of the booster bar. FIG. 5 plotsthe potential bandwidth achieved by the slim radiating system as afunction of the booster bar's width and gap dimensions; the three curves501, 502 and 503 represent the potential bandwidth of a slim radiatingsystem comprising a booster bar having a height of 3.2 mm and a lengthof 7 mm. Curve 501 refers to the booster bar having a depth of 7.5 mm,curve 502 corresponds to a depth of 7 mm and curve 503 is for a depth of6.5 mm. As previously shown in FIGS. 4A and 4B, the potential bandwidthof the slim radiating system depends on the gap that separates thebooster bar from the ground plane layer and the width of the boosterbar; for each of the curves, there is an effective bandwidth regionwhere the most advantageous bandwidth values are achieved.

One way to characterize the radio-frequency performance of the slimradiating system entails the use of a reflection coefficient plot; areflection coefficient of less than −4.4 dB is generally acceptable.FIG. 6 illustrates an example of an acceptable radio-frequencyperformance for a slim radiating system according to the presentinvention. The slim radiating system comprises a booster bar which ischaracterized by a width form factor of 3.125, a height form factor of3.125 and a location factor of 0.96. Curve 601 shows the reflectioncoefficient of the slim radiating system versus frequency, and line 602shows an acceptable reference level for the reflection coefficient. Inthis example, the reflection coefficient is less than −4.4 dB for allthe frequencies of the operating frequency region which covers afrequency range of about 824 MHz to about 960 MHz. Such frequency rangeenables the slim radiating system to be used to cover at least twocommunication frequency bands such as a band from 824 MHz to 894 MHz anda band from 880 MHz to 960 MHz. These two bands are examples of bandsthat can be covered by a slim radiating system; other bands may also behandled by the slim radiating system. In another embodiment, a suitableradio-frequency performance for the slim radiating system corresponds toa reflection coefficient of −6 dB or less for all the frequencies of theoperating frequency range.

FIG. 7 illustrates a preferred example of a slim radiating structureaccording to the present invention suitable for a slim radiating systemconfigured to operate in three frequency regions. The slim radiatingstructure 701 comprises a first booster bar 702, a second booster bar703, a booster element 704 comprising two adjacent booster bars 705 and706, and a ground plane layer 707. As shown in FIG. 3, each booster barcomprises a single standard layer of dielectric material with top andbottom conductive surfaces; in this example the dielectric material hasa height of 3.2 mm. In this example, the first and second booster bars702, 703 have a slim width factor of 3.125, a slim height factor of3.125, and a location factor of 0.96; the booster element 704 has a slimwidth factor of 6.25, a slim height factor of 6.25 and a location factorof 0.96. In general, any suitable shape may be used for the ground planelayer. FIG. 7 illustrates an example of a slim radiating structureaccording to the present invention suitable for a slim radiating systemconfigured to operate in three frequency regions. The ground plane layer707 includes clearance regions that may be used to mount othercomponents of the electronic wireless device, or to adjust the groundplane layer to the shape of the electronic wireless device housing orfor SAR purposes. The ground plane rectangle 708 (represented withdashed lines for illustrative purposes only) is characterized as theminimum sized rectangle that encompasses the ground plane layer 707.That is, the ground plane rectangle is a rectangle whose sides aretangent to at least one point the ground plane layer. In accordance withthe present invention, a first long side of the ground plane layerrefers to a long side of the ground plane rectangle 709 or 710; a secondlong side of the ground plane layer refers to a second long side of theground plane rectangle 710 or 709; a first short side of the groundplane layer refers to a first short side of the ground plane rectangle711 or 712; and a second short side of the ground plane layer relates toa second short side of the ground plane rectangle 712 or 711.

FIG. 8 shows an example of a radio-frequency system 805 coupled to aslim radiating structure 801 via internal conductive paths 802, 803 and804. An example of a suitable slim radiating structure 801 to be coupledto the radio-frequency system 805 is the slim radiating structure shownin FIG. 7. The radio-frequency system 805 comprises a first matchingcircuit 806, a second matching circuit 807, and a third matching circuit808. The first matching circuit 806 is configured to ensure that theslim radiating system is impedance-matched at a first frequency regionto other circuitry coupled via external conductive path 809. The secondmatching circuit 807 is configured to provide impedance matching at asecond frequency region for other circuitry coupled to externalconductive path 810. The third matching circuit 808 is configured toguarantee that the slim radiating system is matched in impedance at athird frequency region at the external conductive path 811. The first,second and third matching networks are therefore configured to ensure anacceptable reference level for the reflection coefficient over anentirety of the first, second and third operating frequency ranges. Eachof the first, second and third matching circuits comprises a network ofpassive components such as inductors and capacitors, which are arrangedwith a suitable architecture like, for instance, an inductor plus an LCnetwork. Other suitable matching circuits may be used to ensure that theslim radiating system is matched in impedance at the operating frequencyranges; other suitable matching circuits may comprise a network ofpassive and/or active components, which may be arranged with othersuitable architectures.

FIG. 9 illustrates the radio-frequency performance of the slim radiatingsystem resulting from the interconnection of the slim radiatingstructure 701 to the radio-frequency system 805. Curve 901 shows thereflection coefficient of the slim radiating system versus frequency ata terminal in the external path 809, curve 902 shows the reflectioncoefficient of the slim radiating system versus frequency at a terminalin the external path 810, curve 903 shows the reflection coefficient ofthe slim radiating system versus frequency at a terminal in the externalpath 811, and line 904 shows an acceptable reference level for thereflection coefficient. In this example, the reflection coefficient 901is less than −4.4 dB for all the frequencies of a first operatingfrequency region 905, the reflection coefficient 902 is less than −4.4dB for all the frequencies of a second operating frequency region 906,and the reflection coefficient 903 is less than −4.4 dB for all thefrequencies of a third operating frequency region 907. The firstoperating frequency region 905 of the slim radiating system covers afirst frequency range of about 698 MHz to about 798 MHz, the secondoperating frequency region 906 of the slim radiating system covers afrequency range of about 824 MHz to about 960 MHz, and the thirdoperating frequency region 907 of the slim radiating system covers athird frequency range of about 1710 MHz to about 2690 MHz. The firstfrequency range enables the slim radiating system to be used to cover atleast three communication bands such as a band from 699 MHz to 746 MHz,a band from 746 MHz to 787 MHz, and a band from 758 MHz to 798 MHz. Thesecond frequency range enables the slim radiating system to cover atleast two communication frequency bands such as a band from 824 MHz to894 MHz and a band from 880 MHz to 960 MHz. The third frequency rangeenables the slim radiating system to cover at least five communicationfrequency bands such as a band from 1710 MHz to 1880 MHz, a band from1850 MHz to 1990 MHz, a band from 1920 MHz to 2170 MHz, a band from 2300MHz to 2400 MHz, and a band from 2496 MHz to 2690 MHz. Other desirablecommunication frequency bands may also be handled by the slim radiatingsystem.

FIG. 10 illustrates another example of a slim radiating structure inaccordance to the present invention; the slim radiating structure issuitable for a slim radiating system that is configured to operate in atleast two frequency regions. The slim radiating structure 1001 comprisesa first booster element 1002 including a first booster bar 1003 and asecond booster bar 1004 adjacent to the first booster bar; the slimradiating structure 1001 further comprises a third booster bar 1005, anda ground plane layer 1006. As shown in FIG. 3, each booster bar may beformed by a single standard layer of dielectric material with top andbottom conductive surfaces. In this example, the dielectric material hasa height of 2.4 mm; the first booster element 1002 has a slim widthfactor of 8, a slim height factor of 10, and a location factor of 0.375;the third booster bar 1005 has a slim width factor of 4, a slim heightfactor of 5 and a location factor of 0.375.

FIG. 11 shows an example of a radio-frequency system 1101 coupled to aslim radiating structure 1102 via internal conductive paths 1103 and1104. An example of a suitable slim radiating structure 1102 to becoupled to the radio-frequency system 1101 is illustrated in FIG. 10.The radio-frequency system 1101 comprises a matching circuit beingconfigured to ensure that the slim radiating system is impedance-matchedto other circuitry coupled via external conductive path 1105 at a firstfrequency region and a second frequency region. The matching network istherefore configured to ensure an acceptable reference level for thereflection coefficient over an entirety of the first and secondoperating frequency ranges. The matching circuit comprises a network ofpassive components such as inductors, capacitors and transmission lines,which are arranged with a suitable architecture as shown in FIG. 11.Other suitable matching circuits may be used to ensure that the slimradiating system is impedance matched at the operating frequency ranges;other suitable matching circuits may comprise a network of passiveand/or active components, which may be arranged with other suitablearchitectures.

FIG. 12 illustrates the radio-frequency performance of the slimradiating system resulting from the interconnection of the slimradiating structure 1001 to the radio-frequency system 1101. Curve 1201shows the reflection coefficient of the slim radiating system versusfrequency at a terminal in the external path 1105, and line 1202 showsan acceptable reference level for the reflection coefficient. In thisexample, the reflection coefficient 1201 is less than −4.4 dB for allthe frequencies of the first and second frequency regions. The firstoperating frequency region of the slim radiating system covers a firstfrequency range of about 698 MHz to about 960 MHz, and the secondoperating frequency region of the slim radiating system coves afrequency range of about 1710 MHz to about 3800 MHz. The first frequencyrange enables the slim radiating system to be used for covering at leastfive communication bands such as a band from 699 MHz to 746 MHz, a bandfrom 746 MHz to 787 MHz, a band from 758 MHz to 798 MHz, a band from 824MHz to 894 MHz, and a band from 880 MHz to 960 MHz. The second frequencyrange enables the slim radiating system to cover at least sevencommunication frequency bands such as a band from 1710 MHz to 1880 MHz,a band from 1850 MHz to 1990 MHz, a band from 1920 MHz to 2170 MHz, aband from 2300 MHz to 2400 MHz, a band from 2496 MHz to 2690 MHz, a bandfrom 3400 MHz to 3600 MHz, and a band from 3600 MHz to 3800 MHz. Otherdesirable communication frequency bands may also be handled by the slimradiating system.

Another example of a slim radiating structure is shown in FIG. 13. Theslim radiating structure 1300 comprises ground plane layer 1302 on aprinted circuit board 1307, and radiation booster 1301 characterized bya slim width factor between 1 and 2, and a slim height factor between 1and 2. The radiation booster 1301 is separated from the ground planelayer by a gap and is characterized by a location factor between 0.5 and2, preferably between 0.5 and 1. The ground plane layer may be inscribedin ground plane rectangle 1306 (in dashed lines for illustrativepurposes only), and the radiation booster may be inscribed in boosterbox 1305 (in dashed lines for illustrative purposes only).

A wireless electronic device comprising a slim radiating system thatincludes slim radiating structure 1300 may advantageously providepenta-band operation: two frequency bands in the first frequency region,like for example the frequency bands corresponding to the GSM 850 andGSM 900 cellular communication standards (i.e. the first frequencyregion comprising the 824 MHz to 960 MHz frequency range), and threefrequency bands in the second frequency region, like for example thefrequency bands corresponding to the GSM 1800, GSM 1900 and WCDMA 2100cellular communication standards (i.e. the second frequency regioncomprising the 1710 MHz to 2170 MHz frequency range). In anotherexample, a device according to the present invention could providetriple-band or quad-band operation with at least two frequency bands inthe first frequency region, and at least another two frequency bands inthe second frequency region, wherein first and second frequency regionsdo not overlap in frequency. Such device could operate, for instance butnot limited to, the GSM 850 and GSM 900 cellular communicationstandards, and the GSM 1800 and GSM 1900 cellular communicationstandards.

FIG. 14A illustrates a radio-frequency system 1400 that comprises afirst port 1401, a second port 1402, and a matching circuit 1403. Suchradio-frequency system is particularly convenient to be used in the slimradiating system of FIG. 2A. Port 1401 may be connected to an internalconductive path (for instance 204 a), and port 1402 may be connected toan external conductive path (for instance 205 a). The matching circuit1403 may be configured to provide impedance matching in at least onefrequency region, or in at least two frequency regions, or in at leastthree frequency regions.

FIG. 14B illustrates another radio-frequency system 1410 comprising afirst port 1411, a second port 1412, a third port 1413, a matchingcircuit 1414, a diplexer 1415, and a conductive path 1416 connecting thematching circuit to the diplexer. In reception, the diplexer 1415 isconfigured to split the signal from conductive path 1416 in a firstsignal extracted at port 1412, preferably comprising the frequenciescorresponding to the first frequency region, and in a second signalextracted at port 1413, preferably comprising the frequenciescorresponding to the second frequency region; in transmission, diplexer1415 combines signals from ports 1412 and 1413 and are extracted inconductive path 1416. The matching circuit 1414 provides impedancematching to the slim radiating system in the first and second frequencyregions. Ports 1412 and 1413 may be respectively connected to first andsecond external paths as shown in FIG. 2D.

FIGS. 15A to 15F show preferred matching circuits configured to provideimpedance matching in at least two frequency regions.

FIG. 15A shows matching circuit 1500 comprising first and second ports1501 and 1502, and a circuit including five stages forming a laddertopology (series-parallel-series-parallel-series). The first stage,which is connected to port 1501, is an inductor in series 1503, thesecond stage is a shunted inductor 1504, the third stage is a capacitorin series 1505, the fourth stage is an inductor in parallel 1506, andthe fifth stage is a capacitor in series 1507, said fifth stage beingconnected to the second port 1502.

In FIG. 15B there is shown matching circuit 1510 comprising six stagesthat form an alternative ladder topology(series-parallel-series-parallel-series-parallel). The first stage (inseries) is connected to the first port 1501 of the matching circuit, andthe sixth stage comprising an inductor in parallel 1511 is connected tothe second port 1502 of the matching circuit.

FIG. 15C depicts another preferred matching circuit 1520 comprising twostages: the first stage comprises a capacitor in parallel 1521, and thesecond stage comprises an inductor in series 1522. A preferred range ofcapacitor values for shunted capacitor 1521 of matching circuit 1520 is0.01 pF to 30 pF.

FIG. 15D shows another preferred matching circuit 1530 comprising aseries inductor 1531 connected to port 1501 and to a series LC resonatorformed by inductive component 1532 a and capacitive component 1532 b.The LC resonator is connected to an LC resonator in parallel, comprisinginductor 1533 a and capacitor 1533 b, and to a series capacitor 1534.The series capacitor is connected to second port 1502 of the matchingcircuit 1530. This matching circuit comprises a single branch formed byfour stages (series-series-parallel-series).

FIG. 15E shows a fifth preferred matching circuit 1540 comprising:inductor 1541 in series connected to port 1501, inductor 1542 inparallel, capacitor 1543 in series, inductor 1544 a and capacitor 1544 bin parallel forming a parallel LC circuit, and capacitor 1545 in seriesconnected to port 1502.

FIG. 15F illustrates another preferred matching circuit 1550 that issimilar to matching circuit 1540 with the difference that capacitor 1545is connected to inductor in series 1551 forming a series LC circuit, andsaid inductor being connected to port 1502 instead of capacitor 1545 asin FIG. 15E.

Inductors 1503, 1531 and 1541 corresponding to the first stage ofmatching circuits 1500, 1510, 1530, 1540 and 1550 may preferably have avalue in the range of 0.1 nH to 80 nH.

Matching circuits 1500, 1510, 1520, 1530, 1540, and 1550 are suitablefor being used as matching circuit 203 a and 203 d shown in FIGS. 2A and2D.

FIG. 16A shows the impedance 1600 of a slim radiating system comprisinga radiation booster, measured at its internal conductive path, when itis disconnected from a radio-frequency system as disclosed in thepresent invention. Points 1601 and 1602 from said impedance correspondto the lowest and highest frequencies of a first frequency region (inthis example, said frequencies are 824 MHz and 960 MHz); and points 1603and 1604 correspond to the lowest and highest frequencies of a secondfrequency region (for this particular example, said frequencies are 1710MHz and 2170 MHz). The impedance 1600 has a substantially large negativereactance, namely the impedance in the first frequency region iscapacitive, for the entire range of frequencies limited by points 1601and 1602, and is also capacitive for the frequencies of the secondfrequency region. The first resonant frequency of said slim radiatingstructure is at a frequency above the highest frequency of the secondfrequency region (as indicated by point 1604).

FIGS. 16B to 16F show the evolution of the impedance of slim radiatingsystem of FIG. 16A after the slim radiating system is connected to aradio-frequency system comprising a matching circuit like 1500 as thestages are added successively to the matching circuit. FIG. 16B showsthe impedance 1610 when the matching circuit only comprises the firststage (an inductor in series). In FIG. 16C, the impedance 1620 of theslim radiating system is shown after adding the inductor in parallel(corresponding to the second stage) to the matching circuit. Theimpedance 1630 from FIG. 16D is obtained after the series capacitor fromthe third stage is added. The impedance 1640 from FIG. 16E is obtainedafter the shunted inductor from the fourth stage is added. And with theaddition of the fifth stage corresponding to another capacitor inseries, the impedance 1650 of the slim radiating system is obtained. Inaddition to the impedance 1650 as shown in FIG. 16F, the reflectioncoefficient 1700, when the slim radiating structure is connected to aradio-frequency system comprising the five-stage ladder matching networkis also shown in FIG. 17. In this particular example, the operatingfrequency range for the radiating system covers a first frequency regionat least comprising the range of frequencies delimited by points 1701and 1702 (824 MHz and 960 MHz respectively), and a second frequencyregion at least comprising the range of frequencies delimited by points1703 and 1704 (1710 MHz and 2170 MHz respectively), wherein said pointsestablish a minimum level of reflection coefficient for a goodradio-frequency performance for this particular example, although inother embodiments said minimum level could be, for example, −4.4 dB.

A ratio between the lowest frequency of the second frequency region andthe lowest frequency of the first frequency region is, for thisparticular case, greater than 1.5 and even greater than 2.0. Inaddition, a ratio between the first resonant frequency of the slimradiating structure measured at an internal path, when disconnected fromthe radio-frequency system, and the lowest frequency of the firstfrequency region is greater than 1.3, also greater than 2.0, and evengreater than 2.4.

FIGS. 18A and 18B show the impedance and reflection coefficient ofanother exemplary embodiment. Such embodiment corresponds to a slimradiating system comprising a slim radiating structure featuring animpedance similar to that of FIG. 16A, and a radio-frequency systemaccording to the present invention. The radio-frequency system comprisesa six-stage matching circuit in a ladder topology, like for examplematching circuit 1510 from FIG. 15B. The impedance 1800, when the slimradiating structure is connected to such radio-frequency system, isshown in FIG. 18A. In said figure, points 1801 and 1802 refer to thelower and higher frequencies of a first frequency region (824 MHz and960 MHz respectively), and points 1803 and 1804 refer to the lower andhigher frequencies of a second frequency region (1710 MHz and 2170 MHzrespectively). The reflection coefficient 1810 of FIG. 18B correspondsto the slim radiating system of FIG. 18A. The operating frequency rangefor a slim radiating system according to this particular embodiment atleast covers a first frequency region including the first rangedelimited by points 1811 and 1812 (824 MHz and 960 MHz), and a secondfrequency region including the second range delimited by points 1813 and1814 (1710 MHz and 2170 MHz).

FIG. 19 shows a radiation booster 1900 comprising conducting surfaces1901 and 1902, a dielectric material 1904 (shown transparent forillustrative purposes only), and a plurality of vias 1903 electricallyinterconnecting the two conducting surfaces 1901 and 1902 (in otherexamples, said conducting surfaces may be interconnected by just onevia). Said radiation booster is a booster bar featuring a slim widthfactor of 3.125, and a slim height factor of 3.125. The booster bar 1900may be used, for example, in slim radiating structure 1300 instead ofradiation booster 1301.

A booster bar such as 1900 is configured to be used in slim radiatingsystems according to the present invention, and in particular in eachand every embodiment of the present invention. As such, a slim radiatingsystem comprising a slim radiating structure, a radio-frequency systemand at least one external conductive path, wherein the slim radiatingstructure comprises a radiation booster like, for example, 1900 and aground plane layer, may be configured to transmit and receiveelectromagnetic wave signals in at least one frequency region, or in atleast two frequency regions. The radio-frequency system comprises amatching circuit configured to provide impedance matching to the slimradiating system in said at least one or at least two frequency regionsat the at least one external path.

FIG. 20 shows a slim radiating structure comprising a radiation booster(e.g. booster bar) 2001, a ground plane layer 2002. There is also showna conductive element 2003 that may advantageously function as aninternal conductive path. The conductive element 2003 is connected toradiation booster 2001, advantageously tuning the input impedance of theradiation booster prior its connection to a radio-frequency system (notshown). The conductive element may improve the efficiency of the slimradiating system comprising said slim radiating structure, or make theslim radiating system operable in more frequency bands in at least onefrequency regions or in at least two frequency regions. In this example,the booster bar features a height of 2.4 mm, a slim width factor of 4, aslim height factor of 5, and a location factor of 0.33. Although theconductive element 2003 is L-shaped, in other examples the conductiveelement may take other forms as well such as a straight I.

The electrical length of conductive element 2003 may be shorter than 10%of the free-space wavelength corresponding to the lowest frequency ofthe first frequency region, and preferably it may be shorter than 5% ofsaid free-space wavelength.

FIG. 21A schematically shows, in a 3D perspective, a test platform forthe characterization of radiation boosters. The platform comprisessubstantially square conductive surface 2101 and connector 2102 (forinstance an SMA connector) electrically connected to the device orelement 2100 to be characterized. The conductive surface 2101 has sideswith a length larger than the reference operating wavelengthcorresponding to the reference frequency. For instance, at 900 MHz, saidsides are at least 60 centimeters long. The conductive surface may be asheet or plate made of copper, for example. The connector 2102 is placedsubstantially in the center of conductive surface 2101.

In FIG. 21B the same test platform of FIG. 21A is schematicallyrepresented in a 2D perspective wherein the conductive surface 2101 ispartially drawn. In this example, the element that is to becharacterized 2100 in FIG. 21A corresponds to booster bar 1900 from FIG.19, which is arranged so that its largest dimension is perpendicular toconductive surface 2101, and one of the first or second conductivesurfaces (1901 or 1902 of FIG. 19) is in direct electrical contact withconnector 2102 (for clearer interpretation of the orientation ofradiation booster 1900, via holes 1903 connecting the first and secondconductive surfaces of the radiation booster are also drawn in FIG.21B). The radiation booster 1900 lies on a dielectric material (notshown) attached to the conductive surface 2101 so as to minimize thedistance between radiation booster 1900 and surface 2101. Saiddielectric material may be a dielectric tape or coating, for example.

FIG. 22 shows a graph of the radiation efficiency and antenna efficiencymeasured in a test platform like the one shown in FIG. 21A and FIG. 21B,when the element 2100 to be characterized is radiation booster 1900. Inthis particular example, the radiation efficiency measured 2201(represented with a solid line) at 900 MHz is less than 5%, and theantenna efficiency measured 2202 (represented with a dashed line) at 900MHz is less than 1%.

The foregoing is merely illustrative of the principles of this inventionand various modifications can be made by those skilled in the artwithout departing from the scope and spirit of the invention. So eventhough that in the illustrative examples described above in connectionwith the figures some particular designs of booster bars with specificvalues for the slim width factor, the slim height factor, and thelocation factor have been used, many other designs of boosters bars inaccordance with the invention having for example different slim widthfactor, slim height factor, and/or location factor could have beenequally used in the slim radiating structures.

What is claimed is:
 1. A radiation booster bar comprising: first andsecond substantially parallel conductive surfaces; a dielectric materialthat supports the first and second conductive surfaces; wherein theradiation booster bar has a slim width factor greater than 2, the slimwidth factor being a ratio between a length and a width of the radiationbooster bar; and wherein the first and second conductive surfaces areconnected at two opposite ends of a longest edge of the first or secondconductive surface so that a first resonant frequency of the radiationbooster bar is higher than a highest frequency of a first frequencyregion of operation of the radiation booster bar.
 2. The radiationbooster bar of claim 1, wherein the dielectric material is air.
 3. Theradiation booster bar of claim 1, wherein the first and secondconductive surfaces are connected by at least one via.
 4. The radiationbooster bar of claim 3, wherein the first and second conductive surfacesare connected at each end of an edge of the first conductive surface bytwo vias.
 5. The radiation booster bar of claim 3, wherein the radiationbooster bar comprises four vias, one at each corner of the firstconductive surface, and wherein the radiation booster bar has arectangular shape and the first and second conductive surfaces aresubstantially the same size.
 6. The radiation booster bar of claim 1,wherein: the radiation booster bar has a first resonance frequencygreater than 3.0 times a reference frequency of 900 MHz, when connectedto a test platform comprising a square conductive surface acting asground plane and having sides measuring 60 centimeters, the radiationbooster bar being mounted close to a central point of the firstconductive surface and extending perpendicularly from the firstconductive surface in a monopole configuration, and being electricallyconnected to a connector; and a radiation efficiency measured for theradiation booster bar in the test platform at the reference frequency of900 MHz is less than 10%.
 7. The radiation booster bar of claim 6,wherein the radiation efficiency measured for the radiation booster barin the test platform at the reference frequency of 900 MHz is less than2.5%.
 8. A radiation booster bar comprising: first and secondsubstantially parallel conductive surfaces; a dielectric material thatsupports the first and second conductive surfaces; wherein the radiationbooster bar has a slim width factor greater than 2, the slim widthfactor being a ratio between a length and a width of the radiationbooster bar; and wherein the first and second conductive surfaces areconnected substantially in the middle of two opposite edges of the firstor second conductive surface such that a first resonant frequency of theradiation booster bar is higher than a highest frequency of a firstfrequency region of operation of the radiation booster.
 9. The radiationbooster bar of claim 8, wherein the first and second conductive surfacesare connected substantially in the middle of the two opposite edges ofthe first or second conductive surface by at least one via.
 10. Theradiation booster bar of claim 9, wherein the first and secondconductive surfaces are also connected at both ends of an edge of thefirst or second conductive surface.
 11. The radiation booster bar ofclaim 8, further comprising two vias between the first and secondconductive surfaces.
 12. The radiation booster bar of claim 11, whereinthe radiation booster bar comprises one via at each corner of the firstconductive surface, and wherein the radiation booster bar has arectangular shape and the first and second conductive surfaces aresubstantially the same size.
 13. The radiation booster bar of claim 8,wherein the first and second conductive surfaces are also connected atboth ends of an edge of the first or second conductive surface.
 14. Theradiation booster bar of claim 13, wherein the first and secondconductive surfaces are connected at each end of an edge of the firstconductive surface by at least one via.
 15. The radiation booster bar ofclaim 13, further comprising first and second vias between the first andsecond conductive surfaces at two ends of an edge of the firstconductive surface.
 16. The radiation booster bar of claim 8, wherein:the radiation booster bar has a first resonance frequency greater than3.0 times a reference frequency of 900 MHz, when connected to a testplatform comprising a square conductive surface acting as ground planeand having sides measuring 60 centimeters, the radiation booster barbeing mounted close to a central point of the first conductive surfaceand extending perpendicularly from the first conductive surface in amonopole configuration, and being electrically connected to a connector;and a radiation efficiency measured for the radiation booster bar in thetest platform at the reference frequency of 900 MHz is less than 10%.17. The radiation booster bar of claim 16, wherein the radiationefficiency measured for the radiation booster bar in the test platformat the reference frequency of 900 MHz is less than 2.5%.
 18. A radiationbooster bar comprising: first and second substantially parallelconductive surfaces connected by at least one via; a dielectric materialthat supports the first and second conductive surfaces; wherein theradiation booster bar has a slim height factor greater than 3, the slimheight factor being a ratio between a length and a height of theradiation booster bar; and wherein the radiation booster bar has amaximum size smaller than 1/15 of the free-space wavelengthcorresponding to a lowest frequency of a first frequency region ofoperation.
 19. The radiation booster bar of claim 18, wherein theradiation booster bar has a maximum size smaller than 1/25 of thefree-space wavelength corresponding to the lowest frequency of the firstfrequency region of operation.